Elevator system

ABSTRACT

An elevator system which automatically reduces the rate of change of acceleration when an elevator car is requested to decelerate before the car reaches the end of its normal acceleration mode. When a stop request is initiated while the car is still accelerating, a modification circuit changes the normal acceleration schedule to reduce the rate of rise of the speed pattern signal. A delay circuit delays the operation of the modification circuit to insure that the modification circuit does not substantially lengthen the time required for the car to reach the landing at which it is to stop.

ilnited States Patent [1 1 Eaputo et al.

[451 Sept. 18, 1973 ELEVATOR SYSTEM Primary Examiner--Bemard A. Gilheany Assistant Examiner-W. E. Duncanson, Jr. AttorneyA. T. Stratton et a1.

[57] ABSTRACT An elevator system which automatically reduces the rate of change of acceleration when an elevator car is requested to decelerate before the car reaches the end of its normal acceleration mode. When a stop request is initiated while the car is still accelerating, a modification circuit changes the normal acceleration schedule to reduce the rate of rise of the speed pattern signal. A delay circuit delays the operation of the modification circuit to insure that the modification circuit does not substantially lengthen the time required for the car to reach the landing at which it is to stop.

11 Claims, 3 Drawing Figures REMAINING CIRCUITS OF FIGAA FROM PATENT NO. 3.207.265

r0 PATTERN MOTOR WINDING 4m 1 4 WAVESHAPE, I

4m. i 37982 TO 379m 395 um on 417 409 1 k \g 413 a UMA DMA 383 3 F L t 88 407377 .377E

M w 3235 UMC omc 3775 42| 425 399 411 379E w L 4|9 387 315 0 A2 xu l DPL6 m g '1'S Dl A3 @LG 0 I 3735 153 2 3m 3730 7 373A A! T "1365 Patented Se t. 18, 1973 2 Sheets-Sheet 2 REMAINING CIRCUITS OF FIG.4A FROM PATENT No. 3,207,265

TO PATTERN MOTOR WINDING 397 40| 1 403 WAVESHAPE, 4m 31952 TO 379m 595 4|7L 4,09 7 383 I 1 ELEVATOR SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates in general to elevator systems, and more specifically to control apparatus for directing the movement modeof an elevator car.

2. Description ofthe Prior Art High speed gearless elevator systems have been developed which provide rapid acceleration, rapid deceleration, and smooth operation over the complete speed range. These characteristics are achieved by a control system which provides a continuous speed pattern signal from stepless pattern transducers which provide the required continuous signals. These continuous signals provide the three basic car movement or control modes, with the first mode being acceleration, the second mode being substantially constant velocity, and the third mode being the slowdown of the elevator car.

The speed and position of an elevator car are controlled by a regulator in which the actual speed and position of the car are compared with a reference pattern signal. A variation between the actual speed and that called for by the reference pattern results in an adjustment for correcting the actual speed of the elevator car.

Apparatus for making such a comparison between the actual speed and that called for by a reference pattern is disclosed in the Oplinger US. Pat. No. 2,874,806, which is assigned to the same assignee as the present application. In the Oplinger patent, the actual speed of the elevator car is determined by the control of an element or device such as a lever which is movable with respect to a supporting structure. The element is electromagnetically coupled to the elevator car motor for the purpose of applying a force acting between the element and the supporting structure which is dependent upon the speed of the elevator car. A second force in opposition to the first force is applied be tween the element and the supporting structure to serve as a reference or pattern representing the desired motor speed. The second force is produced by a second electric or pattern motor which is energized in accordance with the desired speed and position.

The resultantmovement or deflection of the element controls the energization of the elevator car motor and, as a result, the speed and position of the elevator car. Thus, the car motor may be of the direct current type and may have its armature coupled to the armature of a direct current generator to form a variable voltage or Ward Leonard control system. The resultant move ment of the element is utilized to control the field excitation of the direct current generator. In the event a static power supply, such as a dual bridge converter, is used to power the'direct current drive motor, the output of this pattern system is applied to a resistor and the resulting voltage compared with the feedback voltage from a tachometer generator driven by thedrive motor. The difference voltage is used as an error signal which controls the firing angle of the controlled rectifier devices of the dual'bridge converter.

lmprovements in certain characteristics of the apparatus disclosed in the Oplinger patent are disclosed in the Lund et al. US. Pat. No. 3,207,265, which is also assigned to the same assignee as the present application. The Lund et al patent discloses a continuously variable acceleration transducer, which provides a pattern current for the pattern motor,'assuming a Ward Leonard control system, which accelerates the elevator car at a substantially constant rate according to a predetermined acceleration schedule. The acceleration transducer'preferably includes a pair of back-to-back connected controlled rectifiers whose conduction of current is regulated through control of their firing angles by a variable phase gate signal supplied by a pulse generator. The acceleration transducer may include means for shaping the acceleration reference pattern by decreasing the acceleration rate as the elevator car approaches a predetermined speed, such as its maximum velocity.

The apparatus disclosed in the aforesaid Oplinger and Lund et al. patents provides a safe, reliable, highly efficient and accurate elevator system which closely follows the continuous non-linear pattern signals generated by the stepless' transducers. However, one area which could be improved occurs when the car decelerates before completing the acceleration mode of the,

speed pattern, which occurs on a one-floor run, and, depending upon how many floors the car traverses before reaching maximum velocity, on short runs of more than one floor. The Lund et al. patent smooths the transition between the acceleration and constant speed modes, i.e., limits the maximum rate of change of acceleration, which is called jerk, at this transition, but it allows the rate of change of acceleration to exceed this limit when the speed pattern calls for the elevator to change from full acceleration to full deceleration. This more rapid rate of change in acceleration may be slightly uncomfortable to certain passengers, and it would be desirable to change the pattern current when the car is requested to decelerate before reaching the constant velocity mode of its operating cycle.

One of the principal system requirements for an elevator system, however, is for the car to travel between stops in the shortest time possible consistent with passenger comfort. Thus, the modification of the pattern current or normal acceleration schedule when the car is requested to decelerate before reaching zero acceleration, must not substantially increase the length of time between stops. Further, the modification circuitry must be accurate and highly reliable to maintain the high performance standards achieved by present day elevator systems.

SUMMARY- OF THE INVENTION Briefly, the present invention is a new and improved elevator system which reduces the rate of change of acceleration of an elevator car when the car is requested to decelerate while it is still in the acceleration mode. Further, this function is achieved without substantially affecting the time required between stops. t

When the car is requested to decelerate before reaching the constant velocity mode, modification means modifies the normal predetermined acceleration schedule to provide a second acceleration schedule, in which the rate of rise of the pattern current is substantially reduced. This has the effect of rounding out the top of the pattern current curve, and reduces the jerk magnitude accordingly.

The modification means, however, is not immediately effective upon detecting a request to stop which requires deceleration while the car is still in the accelerating mode. If the modification circuit were to become effective as soon as the deceleration request sigwould assume the second acceleration schedule as soon as it leaves the floor at which it was stopped, which would require a prohibitively long time. for the car to complete a. short run.

' The present invention includes delay means which detects where the car is, relative to the first acceleration schedule, when the deceleration request is .re-

' ceived. The length of the run is also automatically considered. The delay means prevents the modification circuit from modifying the'first' acceleration schedule until a predetermined point of the acceleration schedule is reached, thus permitting the car to accelerate normally to a predetermined speed before modifying the acceleration schedule; The predetermined point of the acceleration schedule and predetermined speed is different for each different length of run. For example, the predetermined point of the acceleration schedule is later in the schedule for a two floor run, than for a one floor run, thus allowing the car to reach a greater veloc-,

ity on the two floor run than on a one floor run, before modification occurs.

ln a preferredv embodiment of the-invention, the

- delay means monitors the first acceleration schedule,

and thus the car speed, bydetecting the voltagedr'op across the acceleration device or transducer. The'voltage outputof the acceleration transducer increases I substantially linearly to provide a substantially constant acceleration rate','and the voltage drop across the acceleration transducer decreasessubstantially linearly and is an accurate indication of car speed. Further, the slope 'of the voltage drop'curve is different for different short runs, which automatically adjusts the time from initial car movement until the voltage drop falls. to a predetermined magnitude. This feature enables the car velocit'yto reach greater magnitudes on longer runs e.

fore modification'of the;accelerationschedule is permitted..- Y

j siilrpsscmrrion T E DRAWINGS advantages and uses thereof more readily apparent,

when considered in view of the following detailed description of exemplaryv embodiments, takenwith the accompanying drawings, in which:'

'FIG. 1 isa partially schematic and partially diagram matic view .of an elevatorsystem which may utilize the teachings of theinvention;

FIG. I 2 'is' a schematic diagram of a control circuit constructed according to the teachingsof the inven- F lGiB'is'agraph which plotsi'car speed during theac--' eration transducer during this mode.

DESCRIPTION or PREFERREDEMBODIMENTS- celeration mode, and the'voltage drop across an accelpresentinventionmay be employed in various types of elevato'rcontrol systems. However, forv pur-; poses of example it will be described as appliedto a system which is similar to that disclosed in the Lund et al. patent. Thus, FIGSJ and 2 of the present application are based on FIGS. -1 and 4A, respectively, of theLund et al. patent with-the changes to FIG. 4A of Lund et al.

being'clearly set forth within dashed lines in FIG. 2 of the presentapplication. Components inthis specification which are similar to those inthe Lund et al. patent aregiven'like reference'nur nerals. For the description.

is not necessary in order to understand the present in- I vention, the Lund et al. patent may be referred to, and it is hereby incorporated into this specification by reference.

FIG. 1 is a partially schematic and partially diagrammatic view which illustrates an elevator motor 1 secured to, the upper surface of a floor 3, which may be located in the penthouse of a building or structure being served by the elevator system. The elevator motor 1 has a traction sheave 5 secured to its shaft 6, and an elevator brake 7 is associated with the elevator motor and the traction sheave in a conventional manher. The elevator brake has a shoe which is spring applied by means of a plunger to a brake drum 7d secured to the shaft 6 to hold the traction sheave 5 stationary and is released in response to energization of a solenoid 70. A secondary or idler sheave 9 is secured to the lower surface of the penthouse floor 3. -A control unit 10 is operated by the shaft 6 of motor 1. This control unit is employedin controlling the speed of the motor An elevator car 11 is mounted for movement in a hoistway l3 to'serve thevarious floors or landings of the building.associated"therewith. The elevator car is connected to a counterweight 15 by means of one or more ropes or cables 17, which pass around the traction sheave 5 and the secondary. sheave 9 in a conventional manner. At; each floor served by thev elevator car,

a hoistway or floor door 19 is provided. In addition, the

elevator car has a gate 21 which registers with the hoistway door at any floor at which the elevator'car is stopped. The doors of the gate may be of conventional construction and may be operated automatically in any conventional way.

In order to register calls for floorsdesired by passengers traveling in the elevator car, a plurality of car call buttons 1c through 90 are provided. it is assumed that 40 The invention may be better understood, and further the building served by the elevator car has nine floorsrequiring service.

As. illustrated FIG. 1, an up pushbutton 3U is pro-. vide'd at the third floor 3F for operation by a person de siring transportation in the up direction. A similar pushbutton would be provided. at each of the floors from which a person may desire to travel in theup direction. 'A down pushbiitton 3D .is provided which may be operated by a person desiring to travel in the down direction. A similar pushbutto'n' would be located at each floor from which ap'erson may desire transportation inthe down direction. w

- Control of certain functions of the elevator car is provided by a floor selector 23 which conveniently may be mounted on the penthouse floor 3. This floor selector has two driveinputs supplied thereto. One-is a drive input by an advance motor AM located on the top of the floor selector."l'l 1e seconddrive input is supplied for the purpose of. driving the floor selector in accor dance with movement of the elevator car. Such a drive ple, a drive tape may be provided in a known manner for mechanically driving the selector unit in accordance-with movement of the elevator car. However, in I FIG.' 1, a preferred drive is provided of the selfsynchronous type. Such a drive includes a transmitter or generator SG which is electrically connected to a receiver or motor SM. The transmitter or generator 86 is coupled to the secondary sheave 9 through suitable gearing 25.

The floor selector 23 may be of any suitable type.

Conveniently it may be similar to the floor selector described in the aforesaid Oplinger patent, and such a floor selector is here illustrated generally in FIG. 1. To facilitate consideratiomof the selector, as well as other disclosed circuitry, the following components thereof in FIGS. 1 and 2 are listed which are identical with components bearing the same reference characters in the aforesaid Oplinger patent:

AM advance motor SM motor of self-synchronous drive 35 guide rail 438, 458 synchronous carriages 43A, 45A advance carriages UPL up pawl relay DPL down pawl relay UM up solenoid control unit UMC coil for unit UM UMA magnetic armature for unit UM DM down solenoid control unit DMC coil for unit DM DMA magnetic armature for unit DM U up switch D down switch TSD terminal slowdown relay A acceleration relay 7 For a complete understanding of the floor selector, reference may be made to the aforesaid Oplinger patent and to the Savage US. Pat. No. 2,657,763, which is referred to in the Oplinger patent.

Referring now to FIG. 2, which is a schematic diagram based on FIG. 4A of the Lund et al. patent, there is shown a pair of floor selector transducers comprising solenoid, control units UM and DM are employed for controlling deceleration of the elevator car. Referring for a moment to FIG. 1, the unit UM includes a coil UMC, which is mounted on the advancecarriage 43A, and a soft magnetic armature UMA, which is mounted on the synchronous carriage 43S of the floor selector to an input terminal of a full-wave pattern rectifier359.

The opposite ends of this coil and capacitor are connected through a resistor 360, which has a relatively low resistance, to a terminal 3611. of an autotransformer 361. The transformer 361 is energized from the secondary winding of a voltage regulating transformer 363, which maintains a substantially constant altemating voltage across the transformer 361. The primary 23. The magnetic armature UMA is positioned within the coil UMC when the elevator car is positioned accurately at the floor to provide maximum impedance of the coil. Consequently, relative movement of the ad- 7 vance and synchronous carriage results in movement of the armature relative to the coil UMC for the purpose I of varying the impedance thereof. In a similar manner,

the solenoid control unit DM includes a coil DMC, which is mounted on the advance carriage A, and a soft magnetic armature DMA is mounted on the synchronous carriage 458. Thus, relative movement of the carriage 45Aand 458 results in variation in the impedance of the unit DM. The respective armatures and coils may be configured to provide any desired pattern of variation of coil impedance in response to relative movement of the coils and their armatures.

Returning to FIG. 2, it will be noted that a capacitor 355 is connected across the coil UMC, while a capacitor 357 is connected across the coil DMC. It will be assumed that the design of each of the coils and armatures is such that the variation in total impedance of each coil and its associated parallel capacitor effects a substantially constant rate of deceleration of the elevator car as the associated armature is inserted into the coil. For convenience, the armatures UMA and DMA are illustrated schematically in FIG. 2 for movement winding of the transformer 363 is energized from axsuitable source of alternating current (not shown). The solenoid coil DMC and its associated parallel capacitor 357 are connected similarly to the pattern rectifier 359 and to the autotransformer 361 through make contacts D11 of the down switch D.

It will be observed that the variable voltage autotransformer 319 of the terminal slowdown transducer 311 has its movable contact 317 connected to one input terminal of the pattern rectifier 359. An end terminal of the autotransformer 319 is connected to the other input terminal of the rectifier 359 through break contacts TSD2, the autotransformer being energized from a suitable source of alternating current (not shown). If desired, a suitable filter capacitor 365 may 0 be connected across the output or directcurrent terminaJs of the rectifier 359. e

FIG. 2 also illustrates an acceleration transducer or device which controls the current delivered to the pattern motor winding during acceleration of the elevator car. It is desirable for current in this winding to increase linearly with respect to time, therebybringing the elevator car up to full speed at a substantially constant rate of acceleration. When full speed is reached, it is necessary for the acceleration device to remain fully conductive so that it no longer has control over current in the pattern motor winding.

The acceleration device includes a pair of discontinue ous control type electrical valves such as two solid state controlled rectifiers 371 and 373. Each of these controlled rectifiers has a cathode, a gate and an anode electrode designated by the reference character of the rectifier and the suffixes C, G and A, respectively.

As will be hereinafter described, a delay circuit 500 is connected to be responsive to the voltage drop across the controlled rectifiers 371 and 373. v

It will be noted that the controlled rectifiers 371 and 373 are connected in anti-parallel or back-to-back.

Thus. the anode electrode 371A is connected to the.

cathode electrode 373C, while the anode electrode 373A is connected to the cathode electrode 371C, the

former electrodes also being connected to an input terminal of the pattern rectifier 359 and the latter electrodes also being connected to a movable tap 361A on the autotransformer 3 61. The tap 361A is adjusted vto set the desired operating levelof the pattern current rectifier 359. The gate and cathode electrodes 3716,

and 371C are connected across one secondary winding of a pulse transformer 375, whereas the gate and cathode electrodes 373G and 373C are connected across another secondary winding of the transformer 375.

Control of conduction of current inthe forward'direction by the controlled rectifiers 371 and 373 is accomplished by means of the remaining components associated with the acceleration device. These components form a pulse generator which determines the firing angle of the controlled rectifiers by supplying a variable phase gate signal to the primary winding of the pulse transformer 375. The components preferably include various solid state or semiconductor devices such as a transistor 377, a unijunction transistor 379 and two Zener diodes 383 and 385. Transistor 377 has a base electrode 3773, an emitter electrode 377E and a collector electrode 377C. The unijunction transistor 379 has an emitter electrode 379E, a first base electrode 379B1 and a second base electrode 379B2. The pulse generator employs feedback and thus incorporates means to regulate current buildup in the pattern motor winding to maintain a constant rate of change of such current.

A rheostat 387 may be adjusted to controlthe rate of increase of the output current of the controlled rectifiers 371 and 373. The adjustment of rheostat 387 determines the value of command current I which flows in an error signal resistor 388 in the direction indicated and which is constant for a given setting of the rheostat 387. A resistor 389 may be connected inseries with the rheostat 387 to limit the maximum value to which the current l may be adjusted by means of the rheostat. This current is derived from a supply which includes a transformer 390, a full-wave rectifier 391, a limiting resistor 393, a blocking diode 395, and a filter capacitor 397. Energy for the primary winding of the transformer 390 may be supplied by the autotransformer 361.

As will be hereinafter explained, a modification circuit 502-is connected between rheostat 387 and an output terminal of rectifier 391.

Negative feedback current I, flows through the resistor 388 in the direction indicated and is proportional to the rate of buildup of voltage across the pattern rectifier 359 and thus across the pattern motor winding through the differentiating action of a feedback capacitor 399. It will be observed that one terminalof the capacitor 399 is connected directly to the positive output terminal of rectifier 359, while the other terminal of the capacitor is connected to the negative-output terminal of the rectifier 359 through the resistor 388. A filter capacitor 401 is connected across resistor 388.

Since the command current I and the feedback current I, flow in opposite directions through the resistor 388, the voltage across this resistor is proportional to the difference between these currents, i.e., the net or error signal current l 1,. This voltage through a filter network comprising serially-connected capacitor 403 and resistor 405 controls the magnitude of the collector electrode current in the transistor 377. Thus, the base electrode 3778 of the transistor is connected to one side of the capacitor'403 through a resistor 407, while the emitter electrode 3775 is connected to the other side of the capacitor through a temperature compensating resistor 409. The transistor 377 in turn controls the magnitude of the current which flows to charge a capacitor 411.

When the voltage across capacitor 411, i.e., the voltage between the unijunction transistor emitter and base electrodes 37913 and 37931, reaches a predetermined value for a given value of voltage between the base electrodes 37931 and 37982, the unijunction transistor triggers or fires, and the capacitor 411 discharges through the emitter electrode379E, the base electrode 379Bl and the primary winding of the pulse transformer 375. The voltage pulse produced across the primary winding as a result thereof is applied between the gate and cathode electrodes of the controlled rectifiers 371 and 373 by means of the secondary windings of the pulse transformer. Thus, the controlled rectifier which is forward biased when the pulse is applied will fire or conduct current in the forward direction from its anode to its cathode electrode.

Assuming that the alternating supply voltage has a frequency of 60 hz., if the voltage across the capacitor 411 does not reach the aforesaid predetermined value within 8.3 milliseconds (one-half cycle), of the alternating supply voltage, the unijunction transistor 379 and consequently the controlled rectifiers 371 and 373 will not fire, and the controlled rectifiers will conduct substantially no current. On the other hand, if the voltage across capacitor 411 reaches such predetermined value to fire the unijunction transistor within about 1 millisecond, each of the controlled rectifiers will conduct current fully, for all practical purposes, during that half cycle of the alternating supply voltage when its anode electrode is positive with respect to its cathode electrode.

From the foregoing description, it will be appreciated that the pulse generator controls the conduction of the controlled rectifiers and thus the output of the pattern rectifier 359 to increase smoothly and linearly with respect to time. When each of the controlled rectifiers conducts fully over alternate half cycles of the supply voltage, current supplied by the pattern rectifier to the pattern motor winding arrives at its maximum value, and the elevator car reaches full speed. At this time, the feedback current 1, becomes zero, since the output of the rectifier 359 no longer is changing, and the command current I flowing in the resistor 388 maintains full conduction of each of the controlled rectifiers over alternate half cycles of the supply voltage. During slowdown of the elevator car, the feedback current I, reverses direction due to the discharge of capacitor 399, thus adding to the command current l which also will maintain the controlled rectifiers fully conductive.

It is necessary that the firing pulses applied between the gate and cathode electrodes of the controlled rectifiers by means of the pulse transformer 375 be synchronized with the alternating voltage across the anode and cathode electrodes thereof. Since the autotransformer 361 supplies both the latter voltage and power to the primary winding of the transformer 390, the transformer windings may be connected so that the alternating voltage across the input terminals of the full-wave rectifier 391 is in phase with the voltage across the anode and cathode electrodes of the controlled rectifiers. The Zener diode 385 in conjunction with the resistor 393 functions in a well known manner to clip and regulate the full-wave direct output voltage of the rectifier 391. It will be noted that the blocking diode 395 permits the use of rectifier 391 both for this purpose and as a component for the source of the command current 1 in conjunction with the filter capacitor 397, as previously described. The clipped and regulated voltage is applied between the bases 379B1 and 379B2 of the unijunction transistor 379 through a low resistance temperature compensating resistor 414. When this voltage drops to zero at the end of each half cycle, the unijunction transistor fires and discharges any charge remaining across the capacitor 411. Thus at the start of each half cycle, there is zero voltage across capacitor 41 1.

The acceleration of the elevator car may be decreased by substantially increasing the feedback current I; at a predetermined point. To this end, a capacitor 415 is connected in series with the Zener diode 383 and a portion of a resistor 417 across the output terminals of the pattern rectifier 359. Conveniently, the capacitor 415 may have the same capacitance as the capacitor 399.

The diode 383 has a Zener voltage which is substantially lower than the maximum voltage which appears across resistor 417. When the output voltage of the pattern rectifier 359 reaches this Zener voltage as the elevator car accelerates, the impedance of the Zener diode 383 drops to a relatively low value, the diode conducts current, and capacitor 415 consequently charges at a rate dependent upon the rate of change of the pattern rectifier voltage. Thus, the feedback current l, approximately doubles in magnitude, since the capacitor now is essentially in parallel with the capacitor 399. Inasmuch as the error signal current (l l;) decreases by a comparable amount, the acceleration of the elevator car is halved. The point at which this decrease in acceleration occurs may be adjusted by means of a tap 417A on the resistor 417.

This decrease in acceleration of the elevator car at a predetermined point is useful particularly in those instances where the elevator motor has insufficient commutating capacity. Preferably, the Zener diode 383 is selected and the tap 417A is adjusted to prevent the reduction in acceleration until the elevator car reaches a relatively high speed sothat the car may accelerate at the higher rate during relatively short runs, such as one floor runs. I

in the event that power is applied when the circuit of the pattern motor winding accidentally is open, certain components may be damaged by excessive voltage. A Zener diode 419 may be provided to prevent such damage. A capacitor 423 is connected from the positive output, terminal of the pattern rectifier 359 to the base electrode 3778 of transistor 377. Capacitor 423 provides means for conducting negative feedback current to the base electrode of the transistor which is proportional to the rate of change of the pattern rectifier output voltage. This capacitor is selected to have a relatively low capacitance so that at oscillation rates such negative feedback current is effective for damping, whereas at the normal buildup rateof pattern rectifier output voltage the basic operation of the acceleration device is uneffected.

It will be observed that'the make contacts A2 of an acceleration relay A (not'shown) are connected in parallel with the Zener diode 419. The acceleration relay A is controlled by a cam operated switch. The switch is closed to energize and pick up the relayA when the elevator brake is applied, and is opened to drop out the relay when the brake is released. The acceleration relay A is shown and described in the aforesaid Lund et al. patent. When contacts A2 are closed, the feedback capacitor 399 discharges through resistor 421, and subsequent charging of the capacitor is prevented until the contacts reopen. In addition, a resistor 425 which has relatively low resistance is connected across resistor 388 through make contacts A3 of the acceleration relay A. As a result, when contacts A3 are closed, resistor 388 effectively is shorted by resistor 425. Thus, as

W long as contacts A2 and A3 remain closed, the pulse generator is ineffective for controlling the controlled rectifiers 371 and 373 to accelerate the elevator car.

A resistor 427 is connected from the junction of the controlled rectifier electrodes 371A and 373C to the terminal 361L of the autotransformer 361. This resistor functions to make the normally inductive load of the controlled rectifiers appear as a more resistive load and to improve stability during acceleration of the elevator car.

A capacitor 429 is connected across the input terminals of the pattern rectifier 359. This capacitor has relatively low capacitance and thus presents a relatively high impedance to voltage of the supply frequency across the input terminals of the pattern rectifier. On the other hand, capacitor 429 serves to filter or shunt any undesired high frequency voltage appearing across the input terminals of the pattern rectifier.

The Zener diode 383 and capacitor 399, as hereinbefore explained, may be used to reduce the acceleration of the car at a predetermined point of the acceleration schedule, such as when the elevator motor has insufficient commutating capacity, or when the elevator cycle changes between the acceleration and constant velocity modes. If this feature is used, it would be effective during each acceleration mode of a run, and would change the acceleration rate from a first rate to a lower rate. Regardless of whether this feature is used, however, when the car is requested to decelerate while it is still in the acceleration mode, the rate of change of ac celeration as the car changes from the acceleration to deceleration modes may be uncomfortable for some passengers. The present invention solves this problem by substantially reducing the rate of rise in pattern current, and the reduction may be such as to produce a zero rate of rise if desired. This rounds out the formally triangular shape of the speed; pattern curve for short runs. Further, this modification of the normal acceleration schedule only occurs when the car is called upon to decelerate before'reaching the zero acceleration portion of the speed pattern, and the modification is delayed until a predetermined point of the acceleration schedule is reached, with this predetermined point being different for different lengths of short runs.

More specifically, the delay circuit 500 is connected to be responsive to the voltage across the switching devices 371 and 373, and includes a full-wave rectifier 504 having alternating current input terminals and direct current output terminals, a relay XL, a capacitor 506, a fixed resistor 508, an adjustable resistor or rheostat 510, and break contacts DPLS and UPLS of the down pawl and up pawl relays DPL and UPL, respectively. As explained in the aforesaid Oplinger patent, the up pawl and down pawl relays are energized during up and down travel, respectively, in response to the advance carriage of the floor selector detecting a request to stop at the floor of the advance carriage. Rectifier 504 has its input terminals connected acrossthe backto-back connected switching devices via resistors 508 and 510. Relay XL and capacitor 506 are each connected across the output terminals of rectifier 504. The break contacts UPLS and DLPS are serially connected across adjustable resistor 510.

The modification circuit 502 includes an adjustable resistor 512, a make contact XLl of relay XL, and break contacts DPL6 and UPL6 of down pawl and up pawl relays DPL and UPL, respectively. Adjustable re- 11 sistor 512 is serially connected between the adjustable resistor 387 and an output terminal of rectifier 391. Make contact XLl of relay XL is connected across adjustable resistor 512. The break contacts UPL6 and DPL6 are serially connected across adjustable resistor 512.

When the elevator car is stopped at a landing and the door closing relay is energized, break contacts UPLS and DPLS of the up pawl and down pawl relays VPL and DPL, respectively, will be closed, shorting adjustable resistor 512, break contacts UPL6 and DPL6 of the up pawl and downpawl relays UPL and DPL, respectively, will be closed, shorting adjustable resistor 512, and there will be no voltage drop across the backto-back connected switching devices. Thus, relay XL will be deenergized and its make contact XLl will be open.

When the car is requested to move away from the landing, such as upwardly, to serve a registered car or floor call, the advance motor AM moves the advance carriage 54 in the direction of the requested car movement, such as upwardly, and the appropriate pawl relay is enabled, such as the pawl relay'UPL. Oncezthe advance'car'riage reaches a predetermined spacing from the synchronous carriage, it can then only advance with the'synchronous carriage. The system can be designed such that the elevator car starts to move before the ad vance carriage is fully advanced, or the advance carriage may reach its fully advanced position before the elevator car starts to move, as desired. The up pawl relay will be energized when the advance carriage nears a position corresponding to a floor for whicha call is registered. The car running relay closes to energize the brake solenoid 7C and thus release the elevator brake. The releasing of the elevator brake drops out the acceleration relay A, and its break contacts A1 close to connect the source of alternating potential represented by the'portion of the transformer winding between terminal 361L and selector arm 361A, to the input terminals of the pattern rectifier 359 through the switching devices 37l'and 373. I

The acceleration relay A also opens it make contacts A2 to permit charging of the feedback capacitor 399 and opens its make contacts A3 to disconnect the low resistance resistor 425 across the error signal resistor 388. As a result, the acceleration device pulse generator, comprising the transistor 377, the unijunction transistor 379, the Zener diode 385 and their associated components, applies a'variable phase gate signal betwe en'the gate and cathode electrodes of the controlled rectifiers 371 and 373 through the pulse transformer 375. Thus, the controlled rectifiers supply a linearly increasing current to the pattern motor winding of the v pattern motor by means of the pattern rectifier 359. As

hereinbefore described, the rate of the build-up of the pattern current is controlled by the setting of rheostat 387.

As soon as break contact A1 closes, the full source voltage appears across the switching devices 371 and 373, and this voltage, as rectified by rectifier 504, picks up relay XL. The closed contacts UPLS and DPLS shunting adjustable resistor 510 assures the pick-up of relay XL without interference due to the setting of adjustable resistor 510. Make contacts XLl close to shunt adjustable resistor 512.

lf no calls are detected by the advance carriage before the predetermined acceleration scheduleset by adjustable resistor 387 is completed, the speed of the elevator car builds-up during the acceleration mode along a curve 520, as shown in FIG. 3, and enters the constant velocity mode indicated by curve portion 522. If the car is requested to decelerate after the constant velocity mode is reached, it decelerates according to a predetermined deceleration schedule, such as along curve portion 524, without a sharp increase in the rate of change of acceleration.

If a call is detected which requires deceleration before curve portion 522 is reached, the slowdown pattern merges into the acceleration pattern to produce an operating cycle with no constant speed component, and possibly a higher than comfortable rate of change of acceleration. In this instance, the present invention functions to reduce the rate of rise of pattern current, and thus reduce the rate of change of acceleration. This is accomplished by setting adjustable resistor 512 to a value, which when serially inserted into the circuit which includes rheostat 387, drops the value of current 1,, to produce the desired rate of rise of pattern current. In a preferred embodiment,adjustable resistor 512 is set such that when it is inserted into the circuit it provides a zero rate of rise of pattern current.

Adjustable resistor 512 is inserted into the circuit, assuming that contact XLl of relay XL is open, when a call is detected by the advance carriage and the up or down pawl relay is energized, which opens contacts UPL6 or DPL6. Contact XLl functions to delay the modification of the predetermined normal acceleration schedule, as will be hereinafter described. If a call is detected after the constant velocity mode has been reached, the insertion of adjustable resistor 512 into the pulse circuit has no circuit effect, since the acceleration device is no longer in control of the pattern rectifier 359.

The function of delay circuit 500 is to assure that the elevator car reaches an elevated speed before modifying the acceleration schedule by reducing the rate of rise of pattern current. If the detection of a call during the acceleration mode were to automatically modify the acceleration schedule, a short run, some as a onefloor run, would require an unduly long period of time to complete, as the car speed would almost immedithe voltage drop across the switching devices of the acceleration transducer, to car speed. As the car speed linearly increases with time during the acceleration mode, such as shown by curve 520 in FIG. 3, the voltage across the switching devices reduces from the selected magnitude of autotransformer 361 to substantially zero. Thus, as the car speed increases, the voltage across the switching devices drops, and this voltage is used to energize relay XL. When relay XL is energized, its make contacts XLl prevent the modification circuit 502 from being effective, even though a call has been detected and thecircuit which includes break contacts UPL6 and DPL6 is open.

If a call is detected by the advance carriage, either contact UPLS or contact DPLS will open to enable the delay circuit by inserting adjustable resistor 510 into the circuit of relay XL. The setting of adjustable resistor 510 is selected to drop out relay XL at that voltage which allows sufficient time to change from acceleration to deceleration comfortably. For example, the adjustable resistor 510 may be set to drop out at a voltage level indicated by dashed line 528 in FIG. 3, with the car speed 'at this voltage level depending upon the length of the run. If, when a call is detected, the acceleration schedule is still in an early portion thereof, wherein the voltage across the switching devices is above level 528, the delay circuit 506) delays the operation of the modification circuit 502. If, when a call is detected, the acceleration schedule is already in a predetermined terminal portion thereof wherein the voltage across the switching devices is below level 528, the opening of contacts UPLS or DPLS will insert adjustable resistor 510 into therelay circuit, and cause it to drop out. Thus, contacts XLI will open, and since either contacts UPL6' or DPL6 have already opened, resistor 512 will be effective in reducing the rate or rise of pattern current, and the car speed will change more gradually between the acceleration anddeceleration modes, to provide an effective limit on the maximum rate of change of acceleration. Since the advance carriage usually advances to the limit as soon as the car starts to leave a floor, unless calls are detected, in the usual operation of the disclosed invention, the delay circuit will always be effective as the request to decelerate will be known, and the length of the short run will be known about the time the car starts to move.

For example, velocity curves 532, 534 and 536 in FIG. 3 represent progressively longer runs for a high speed elevator system which requires more than three floors to reach the constant velocity mode of its cycle. Thus, velocity curves 532, 534 and 536 may represent one, two and three floor runs, respectively. On a onefloor run, the advance carriage detects the call about the time the car is leaving the adjacent floor. The appropriate pawl relay opens its contacts to insert resistor 510 into the circuit of relay XL, but the voltage across relay XL will be above its drop out value, and the modification circuit 502 is ineffective until the voltage across the switching devices drops to point 532" on the voltage versus time curve 532 shown in FIG. 3. When point 532 is reached, relay XL will drop out and resistor 512 will then modify the rate of rise of pattern current; Instead of following the velocity curve 532 through peak 540, the effect of resistor 512 is to flatten out the peak and provide the dash line curve portion 542 shown in FIG. 3.

On a two floor run, illustrated by curve 534, the delay circuit delays the modification of the acceleration schedule until voltage curve 534 drops to level 528, resulting in the modified velocity curve portion 544, which replacesportion 546. It will be noted that the slope of the voltage curve 534' for the two floor run is different than the slope of the voltage curve 532' for the one floor run. Theslope of the voltage curve depends upon the length of the run. This is due to the fact that the UP and DOWN solenoid control units UM and DM have a lower impedance when the selector is advanced a greater distance, and the controlled rectifiers 37! and 373, which are in series with these solenoid control units, have their firing angle advanced at a slower rate to produce a linear buildup of pattern current with time. v

on the three floor run, illustrated by curve 536, the voltage curve 536' has a different slope than for the one and two floor runs, as hereinbefore explained, with the delay circuit 500 allowing the car to reach a still highervelocity before the modification circuit 512 becomes effective. The modification circuit replaces curve portion 548 with the flatter portion 550.

If a call is not detected before the car speed reaches constant velocity, relay XL merely drops out at its normal drop out voltage. A mercury wetted relay which has a normal pick-up current of about five or six times its normal drop out current has been found to be satisfactory for relay XL.

In summary, there has been disclosed a new and improved elevator system which provides improved performance during those short trips where the normal full speed component of the operating cycle'is not reached, and the acceleration and deceleration patterns merge. The normally high rate of change of acceleration experienced during this type of operating cycle is modified to change the car speed more gradually during the tran-' sition between operating modes. Further, the modification of the normal acceleration schedule is delayed for a time which depends upon the length of the short run, in order to maintain as short a trip time on these short runs as possible, consistent with passenger comfort. We claim as our invention: 1. An elevator system, comprising: an elevator car, a structure having spaced landings to be served by said car, motive means for moving the car relative to said structure to serve the landings, car control means providing a speed pattern reference signal for said motive means which directs the movement mode of said car, said car control means including acceleration means which provides an acceleration mode, accelerating the car according to a first predetermined acceleration schedule, call means operable to provide a stop request signal when said car is to stop at a landing," modification means responsive to a'stop request signal initiated during a predetermined terminal portion of said first acceleration schedule to modify the speed pattern reference signal to provide a second predetermined acceleration schedule,

and delay means operative when a stop request is ini-' with the delay means being responsive to the voltage across the acceleration means, said delay means preventing the modification of the speed pattern reference signal when the-voltage across the acceleration means exceeds a predetermined magnitude.

3. The elevator system of claim 1 wherein thecar control means includes rectifier means and a source of alternating potential, and the acceleration means includes a pair of back-.to-back connected switching devices connected in series with said rectifier meansand said source of alternating potential, and control means for firing said switching devices to provide an output voltage from said rectifier means which provides the desired acceleration schedule, with the delay means being responsive to the voltage across said switching devices.

4. The elevator system of claim 3 wherein the acceleration means increases the voltage applied to therectifier means substantially linearly, reducing the voltage drop across the switching devices substantially linearly, said delay means preventing the operation of the modification means while the voltage drop is above a predetermined magnitude.

5. The elevator system of claim 4 wherein the delay means includes a relay responsive to the voltage across the switching devices, and impedance means which elavates the drop out voltage of said relay to the desired level.

6. The elevator system of claim 5 including means rendering said impedance means for elevating the drop out voltage effective only when a stop request signal is initiated, facilitating the pickup of said relay at the start of the acceleration mode.

7. The elevator system of claim 5 wherein the relay,

when it drops out at its elevated drop out voltage modities the control means to slow down the rate of rise of pattern current to reduce the rate of change of acceleration as the speed pattern changes from an acceleration mode to a deceleration mode.

8. The elevator system of claim 7 wherein the control means is modified to provide a zero rate of rise of pattern current.

9. The elevator system of claim 4 including means providing a different slope of the linear voltage drop curve for different lengths of short runs, to enable the elevator car to reach a high speed on a larger run than on a shorter run, before the voltage drop reaches the predetermined magnitude.

10. An elevator system, comprising:

an elevator car,

a structure having spaced landings to be served by said car,

motive means for moving the car relative to said structure to serve the landings,

car control means providing a speed pattern reference signal for said motive means which directs the movement mode of said car,

said car control means including acceleration means which provides an acceleration mode, accelerating the car according to a first predetermined acceleration schedule, said acceleration means operating such that the voltage drop across it is reduced as the elevator car increases in velocity,

call means operable to provide a stop request signal when said car is to stop at a landing,

modification means effective when the elevator car initiates deceleration in response to a stop request, prior to the completion of said first acceleration schedule, to provide a second predetermined acceleration schedule,

and delay means preventing the modification of the speed pattern reference signal when the voltage drop across said acceleration means is above a predetermined magnitude.

II. The elevator system of claim 10 wherein the voltage drop across the acceleration means during the acceleration mode is substantially linear, with the slope of the voltage drop curve being responsive to the length of the run, when deceleration of the car is initiated prior to the end of the first acceleration schedule, to lengthen the time required for the voltage across the acceleration means to drop to the predetermined magnitude as the length of the run increases. 

1. An elevator system, comprising: an elevator car, a structure having spaced landings to be served by said car, motive means for moving the car relative to said structure to serve the landings, car control means providing a speed pattern reference signal for said motive means which directS the movement mode of said car, said car control means including acceleration means which provides an acceleration mode, accelerating the car according to a first predetermined acceleration schedule, call means operable to provide a stop request signal when said car is to stop at a landing, modification means responsive to a stop request signal initiated during a predetermined terminal portion of said first acceleration schedule to modify the speed pattern reference signal to provide a second predetermined acceleration schedule, and delay means operative when a stop request is initiated during the first acceleration schedule but prior to the predetermined terminal portion thereof, said delay means delaying the modification of the speed pattern reference signal until said terminal portion of the first acceleration schedule is reached.
 2. The elevator system of claim 1 wherein the voltage across the acceleration means during the acceleration mode is inversely proportional to the speed of the car, with the delay means being responsive to the voltage across the acceleration means, said delay means preventing the modification of the speed pattern reference signal when the voltage across the acceleration means exceeds a predetermined magnitude.
 3. The elevator system of claim 1 wherein the car control means includes rectifier means and a source of alternating potential, and the acceleration means includes a pair of back-to-back connected switching devices connected in series with said rectifier means and said source of alternating potential, and control means for firing said switching devices to provide an output voltage from said rectifier means which provides the desired acceleration schedule, with the delay means being responsive to the voltage across said switching devices.
 4. The elevator system of claim 3 wherein the acceleration means increases the voltage applied to the rectifier means substantially linearly, reducing the voltage drop across the switching devices substantially linearly, said delay means preventing the operation of the modification means while the voltage drop is above a predetermined magnitude.
 5. The elevator system of claim 4 wherein the delay means includes a relay responsive to the voltage across the switching devices, and impedance means which elavates the drop out voltage of said relay to the desired level.
 6. The elevator system of claim 5 including means rendering said impedance means for elevating the drop out voltage effective only when a stop request signal is initiated, facilitating the pick-up of said relay at the start of the acceleration mode.
 7. The elevator system of claim 5 wherein the relay, when it drops out at its elevated drop out voltage modifies the control means to slow down the rate of rise of pattern current to reduce the rate of change of acceleration as the speed pattern changes from an acceleration mode to a deceleration mode.
 8. The elevator system of claim 7 wherein the control means is modified to provide a zero rate of rise of pattern current.
 9. The elevator system of claim 4 including means providing a different slope of the linear voltage drop curve for different lengths of short runs, to enable the elevator car to reach a high speed on a larger run than on a shorter run, before the voltage drop reaches the predetermined magnitude.
 10. An elevator system, comprising: an elevator car, a structure having spaced landings to be served by said car, motive means for moving the car relative to said structure to serve the landings, car control means providing a speed pattern reference signal for said motive means which directs the movement mode of said car, said car control means including acceleration means which provides an acceleration mode, accelerating the car according to a first predetermined acceleration schedule, said acceleration means operating such that the voltage drop across it is reduced as the elevator car increases in velocity, call mEans operable to provide a stop request signal when said car is to stop at a landing, modification means effective when the elevator car initiates deceleration in response to a stop request, prior to the completion of said first acceleration schedule, to provide a second predetermined acceleration schedule, and delay means preventing the modification of the speed pattern reference signal when the voltage drop across said acceleration means is above a predetermined magnitude.
 11. The elevator system of claim 10 wherein the voltage drop across the acceleration means during the acceleration mode is substantially linear, with the slope of the voltage drop curve being responsive to the length of the run, when deceleration of the car is initiated prior to the end of the first acceleration schedule, to lengthen the time required for the voltage across the acceleration means to drop to the predetermined magnitude as the length of the run increases. 